<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    </head>
    <body>
        <div class="list" style="display:flex ; text-align:center;">

        </div>
    <button class="prev">上一页</button>
    <button class="next">下一页</button>
    <script>

        var page = 1;
        function objToSearchString(obj){
            var str = '';
            for( var key in obj ){
                str += `${key}=${obj[key]}&`
            }
            return str.slice(0,str.length-1);
        }

        function ajax( method, url , params , cb ){
            var xhr = new XMLHttpRequest();
            xhr.open(method, url+"?"+ objToSearchString(params) );
            xhr.onreadystatechange = function(){
                if(xhr.readyState == 4){
                    cb( JSON.parse( xhr.responseText )  );
                }
            }
            xhr.send();
        }
        
        //点击上一页
        document.querySelector('.prev').onclick = function(){
            if( page > 1 ){
                ajax('get',`https://yantianfeng.com/api/emotion`, {page:--page,count:10} , function(data){
                    var str = data.emotions.map((item,index)=>{
                        return `<div> <img src="${item.url}" /> <div> ${item.title} </div> </div>`
                    }).join('')
                    document.querySelector('.list').innerHTML = str;
                });
            }
        }
        
        //点击下一页
        document.querySelector('.next').onclick = function(){
            if( page < 4 ){
                ajax('get',`https://yantianfeng.com/api/emotion`, {page:++page,count:10} , function(data){
                    var str = data.emotions.map((item,index)=>{
                        return `<div> <img src="${item.url}" /> <div> ${item.title} </div> </div>`
                    }).join('')
                    document.querySelector('.list').innerHTML = str;
                });
            }
        }
        
        
    </script>
    
</body>
</html>